For a printed wiring board for electronic appliances, a laminated board using a resin composition mainly composed of an epoxy resin is widely used. Recently, with the tendencies that a pattern becomes finer due to increase in mounting density in electronic appliances, a surface mounting system is more established, a signal propagation velocity becomes higher, and a frequency of signals used becomes higher, a development of printed wiring board materials having a low dielectric constant, a low dielectric loss and an improved heat resistance is strongly desired.
On the other hand, it is required to avoid the use of halogen-based flame retardant in resin compositions in view of its adverse affect on environments. Therefore, a halogen-free alternative material having excellent flame retardancy is also strongly desired.
With respect to a resin composition mainly composed of a resin other than an epoxy resin, studies are made on a resin composition and the like using styrene or a polyphenylene ether resin. Examples of the resin composition or laminated board using a polyphenylene ether resin are disclosed, for example, in Japanese Unexamined Patent Publication No. Hei 4-076018, Japanese Unexamined Patent Publication No. Hei 4-076019, Japanese Unexamined Patent Publication No. Hei 7-247415, Japanese Unexamined Patent Publication No. Hei 7-258537, Japanese Examined Patent Publication No. Hei 6-092532, Japanese Examined Patent Publication No. Hei 6-092533, Japanese Examined Patent Publication No. Hei 6-092534, etc. Examples of the resin composition or laminated board using a styrene resin and a polyphenylene ether resin are disclosed, for example, in Japanese Unexamined Patent Publication No. Hei 4-088054 and Japanese Unexamined Patent Publication No. Hei 7-268205. However, a halogen-based flame retardant is used in any of these resin compositions or laminated boards.
Improvement in properties is also attempted by combining an epoxy resin with another resin. For an example of a resin composition or laminated board using an epoxy resin as a curing agent and using a copolymer resin composed of styrene and maleic anhydride, for example, Japanese Unexamined Patent Publication No. Sho 49-109476 describes a flexible printed wiring board using a flexible epoxy resin and a copolymer resin composed of styrene and maleic anhydride, wherein a reactive epoxy diluent and an acrylonitrile-butadiene copolymer are essential for imparting flexibility to the printed wiring board. Japanese Unexamined Patent Publication No. Hei 1-221413 describes an epoxy resin compound comprising an epoxy resin, a copolymer resin having an acid value of 280 or more, which is obtained from an aromatic vinyl compound and maleic anhydride, and dicyandiamide. Further, Japanese Unexamined Patent Publication No. Hei 9-025349 describes a prepreg and a laminated board material for electrical appliances, containing a brominated epoxy resin, a copolymer resin composed of styrene and maleic anhydride (epoxy resin curing agent), a styrene compound, and a solvent. Japanese Unexamined Patent Publications No. Hei 10-017685 and No. Hei 10-017686 describe a prepreg and a laminated board material for electrical appliances, containing an epoxy resin, a copolymer resin composed of an aromatic vinyl compound and maleic anhydride, and a phenolic compound. Japanese Unexamined national Patent Publication (kohyo) No. Hei 10-505376 describes a resin composition, a laminated board, and a printed wiring board, containing an epoxy resin, a carboxylic anhydride-type cross-linking agent for epoxy resin, and an allyl linkage-forming compound. However, these materials are not satisfactory in characteristics required with the tendencies to a finer pattern forming and a higher frequency of signals, for example, low dielectric loss, high heat resistance, high moisture resistance, and high adhesiveness to a copper foil. In addition, these materials have problems that a halogen-based flame retardant compound is used or flame retardancy is low.
For the halogen-free-type flame retardant, a phosphorus-containing compound is usually used. Examples thereof include condensed phosphates such as red phosphorus, phosphoric acid, triphenyl phosphate, etc.; phosphoric acid derivatives such as ammonium polyphosphate; and reactive phosphorus-containing compounds such as phosphorus-containing epoxy resin and hydroxyl group containing phosphorus compound. However, when flame retardancy is imparted using these phosphorus-containing compounds, an adverse affect is liable to be exerted on dielectric constant, dielectric loss, heat resistance, moisture resistance or electrolytic corrosion resistance.
The object of the present invention is to provide a thermosetting resin composition which is excellent in all of dielectric property, dielectric loss, heat resistance, flame retardancy, moisture resistance, and adhesiveness to a copper foil, even though the halogen-free flame retardant is used in view of the above-described problems; and a prepreg and laminated board using the resin composition.